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Debunking Scala myths

Asked 2010-10-13T16:53:46.880
61

What are the most commonly held misconceptions about the Scala language, and what counter-examples exist to these?

UPDATE

I was thinking more about various claims I've seen, such as "Scala is dynamically typed" and "Scala is a scripting language".

I accept that "Scala is [Simple/Complex]" might be considered a myth, but it's also a viewpoint that's very dependent on context. My personal belief is that it's the very same features that can make Scala appear either simple or complex depending oh who's using them. Ultimately, the language just offers abstractions, and it's the way that these are used that shapes perceptions.

Not only that, but it has a certain tendency to inflame arguments, and I've not yet seen anyone change a strongly-held viewpoint on the topic...

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Myth: this.type refers to the same type represented by this.getClass.

As an example of this misconception, one might assume that in the following code the type of v.me is B:

trait A { val me: this.type = this }

class B extends A

val v = new B

In reality, this.type refers to the type whose only instance is this. In general, x.type is the singleton type whose only instance is x. So in the example above, the type of v.me is v.type. The following session demonstrates the principle:

scala> val s = "a string"
s: java.lang.String = a string

scala> var v: s.type = s
v: s.type = a string

scala> v = "another string"
<console>:7: error: type mismatch;
 found   : java.lang.String("another string")
 required: s.type
       v = "another string"
answered 2010-12-02T20:32:01.993

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